Gas nozzle for a welding torch, welding torch, and cleaning device for a welding torch

ABSTRACT

The invention relates to a gas nozzle and to a welding torch equipped with the gas nozzle, a nozzle assembly and with a contact tube that have an artificially produced patina layer for the purpose of reducing the adhesion of welding spatters at least on a partial area of the surface thereof. The invention also relates to a cleaning device for welding torches having a brush provided with bristles. These bristles are made of a very soft elastic material, preferably plastic, and abrasive grains are embedded in the bristles.

The invention relates to a gas nozzle for a welding torch, which is madeof copper or a copper alloy, as well as a welding torch including a gasnozzle, a nozzle assembly and a contact tube, wherein the gas nozzleand/or the nozzle assembly and/or the contact tube are made of copper ora copper alloy.

The invention further relates to a cleaning device for a welding torchand, in particular, its gas nozzle, which includes a brush provided withbristles for cleaning the welding torch of weld spatter.

During a welding procedure, welding torches are contaminated by moltenmetal spatters. Said metal spatters deposit on the exterior of thehousing of the gas nozzle of the welding torch and even within the gasnozzle, solidifying there. As a result, the flow of the protective gasthrough the gas nozzle will be disturbed by the deposited metal spattersin a manner that atmospheric air too will reach the welding site, thusadversely affecting the welding process. It may, moreover, happen thatshort-circuits are caused by such welding spatters. For a high-qualityweld, a perfectly functioning and largely clean welding torch is,therefore, essential. As a result, welding torches are cleaned ofadhering spatters at regular intervals. During cleaning, the weldingtorch will not be available for welding operations. It is, therefore,aimed to perform cleaning as rapidly as possible.

From DE 44 26 303 C1 a non-stick agent against weld spatter is, forinstance, known, which is comprised of a solution of a glycerol ester ofan unsaturated C18-C20-fatty acid in a methyl or ethyl ester of such afatty ester. That non-stick agent is applied to those parts of a weldingtorch, where the adherence of weld spatter is to be prevented.

It is, furthermore, feasible according to DE 195 07 472 C2 to apply acoating to the gas or current nozzle of a protective-gas weldingapparatus, wherein the gas or current nozzle is made of a metal that iscoated with a protective layer containing graphite and a polymerreleasing carbon under heat exposure and/or a heat-resistant polymer.

A welding torch and a current nozzle or contact tube where a specialcoating is applied are known from DE 201 00 126 U1. The welding torchcomprises an internally arranged nozzle assembly to whose end sectionfacing the welding region a hollow current nozzle is attached, wherein ametallic non-stick and reflexion coating is provided on at least aportion of the surface of the current nozzle. The coating comprisessilver as its main component.

Various mechanical methods have been available for the cleaning of awelding torch and, in particular, its gas nozzle, contact tube andnozzle assembly. Thus, deposits, i.e. weld spatters on the weldingtorch, are, for instance, removed by the aid of metal brushes, blades orthe like. During mechanical cleaning, the structural components of thewelding torch will be damaged by mechanical action, and their servicelives will be reduced accordingly.

From EP 0 765 204 B a device for cleaning the heads or gas nozzles ofwelding torches is known, which device comprises an open container towhich an ultrasonic generator is connected, said ultrasonic generatorproducing ultrasonic waves in a liquid. Furthermore, a rotary tool isarranged within the container. The tool may be comprised of a steel wirebrush or a metal brush, in which the bristles of the brush are made ofsteel. The use of the brush, however, presupposes that the ring orspatter be separated from the housing by ultrasonic vibrations, i.e.ultrasonic waves, in a manner that the ring or spatter drops off thehousing during brushing.

Furthermore, a device for cleaning a gas nozzle of a welding torch isknown from DE 33 39 547 C, in which the outer contour of the brush isadapted to the shape of the gas nozzle inner surface to be cleaned. Inthat case the brush is comprised of a bristle strip arranged on acylindrical shaft, which cylindrical shaft has a concentric nose ofreduced outer diameter to fit into the bore that serves to fasten thegas nozzle to the welding torch. The shaft further comprises a handlestick such that the device can be manually inserted into the gas nozzleby a user so as to enable the cleaning of the gas nozzle or weldingtorch by the user.

Basically, it should be noted that there is still a plurality of otherdevices for cleaning gas nozzles of welding torches, by which cleaningis effected by the aid of crushing tools such as, for instance, millingtools or cutting tools. In those cases, the tool is introduced into thegas nozzle, and the spatter is peeled off the gas nozzle by such a tool,i.e., a miller or cutting element.

The systems known from the prior art involve the disadvantage that suchmechanical cleaning devices will only enable the successful cleaning ofgas nozzles if the spatter consists of a solid material and, inparticular, steel or a steel alloy, which means that a welding processfor joining workpieces of steel or steel alloys is performed such thatthe spatter will be formed of those materials. Otherwise, theapplication of the usual tools known from the prior art, i.e., a millingtool, a cutting tool or metal brushes, is impossible, since in weldingprocesses using soft materials such as, for instance, aluminum, thespatter forming of aluminum cannot be readily removed from, or peeledoff, the gas nozzle. In those cases, it will in fact happen that thespatter consisting of aluminum will not readily separate from the gasnozzle as a whole, but rather be spread by rubbing or smeared by thetool, which is why the cleaning quality of known tools leaves much to bedesired.

The object of the present invention consists in reducing thespatterability of welding torches. Another object of the inventionresides in providing an above-mentioned cleaning device for weldingtorches and, in particular, the gas nozzles of the same, especially whenemploying an aluminum welding process, by which the cleaning qualitywill be substantially improved, thus assisting automated cleaning, whichis particularly suitable for welding robot applications. In addition,the device is to be constructed as simple and cost-effective aspossible.

The object according to the invention is achieved in that the gas nozzlecomprises an artificially produced patina layer at least on a partialarea of its surface.

The object of the invention is, however, also achieved in that, in awelding torch, the gas nozzle and/or the nozzle assembly and/or thecontact tube comprise an artificially produced patina layer at least ona partial area of the respective surface.

Among all surface coating methods, the generation of an oxidic layerfrom the parent metal (patina layer) yields a layer that exhibits theoptimum adhesive properties, because the layer is not applied to thesurface but stepwisely formed chemically of the parent metal already ona molecular plane at the grain boundaries of the texture.

This offers the advantage that the artificially produced patina layer inthe event of a gas nozzle made of copper, or the copper components of awelding torch, constitutes a layer that is characterized by the presenceof (OH)-groups. This oxygen compound creates a high surface tension, anelevated temperature resistance and a reduced wettability. In addition,this oxidation film on the copper surface prevents aluminum melt frompenetrating into the surface pores and, hence, adhering thereto. Due tothis effect, cleaning of the components is substantially facilitatedtoo, since the weld spatters are actually very easily separated from thepatina layer. Thus, hardly any damage to the surface will occur duringcleaning of the components, whose service lives will consequently belargely increased. An essential advantageous, above all, resides in thefact that a very low spatter adherence is reached when using parts withpatina layers in an aluminum welding process, since aluminum does notcombine with the patina layer and the weld spatter will, thus, only verypoorly adhere.

Further characteristic features are described in claims 3 and 4. Theadvantages resulting therefrom are to be taken from the description.

The object of the invention is further achieved in that the bristles ofthe brush of a cleaning device are formed of a very soft, elasticmaterial, preferably a synthetic material, and that abrasives areembedded in said bristles. As a result, new grain or abrasives areconstantly released from the bristles due to the wear of the brushes,thus providing a uniform abrasive effect over an extended period oftime. It is, thus, also ensured that a constantly high cleaning qualitywill be achieved. Furthermore, the synthetic brushes are highly elasticand flexible, thus enabling better cleaning than metal brushes on sitesthat are difficult to accede like the interior of the welding torch,since the brushes are able to adapt to the shape of the gas nozzle. Thiseffect, in particular, is achieved by the centrifugal force occurring atelevated speeds. A very essential advantage resides in that the surfacesof the parts to be cleaned, such as the gas nozzle, the contact tube orthe nozzle assembly, will not be damaged or scratched to the same extentas by the tools known from the prior art and, in particular, steelbrushes. The most essential advantage, however, resides in that, by sucha configuration of the brush, the spatter adhering to the gas nozzle orwelding torch is no longer simply peeled off as happens by millingtools, cutting tools or steel brushes, but the spatter is completelyseparated as a whole without any mechanical damage to the wear partsurfaces.

In an advantageous manner, the bristles are provided with a coating inwhich abrasives are embedded.

Yet, a configuration according to claim 7 is of advantage too, becauseit enables the interior of the gas nozzle and the outer surface of thegas nozzle to be cleaned simultaneously in a single operation.

A configuration according to claim 8 is advantageous in that thebristles are able to reach far into the gas nozzle, i.e., into theinterior of the gas nozzle, thus enabling very deep cleaning. It is alsoensured that, due to the length of the bristles, their flexibility willbe increased such that the bristles will readily adapt to the parts tobe cleaned, thus providing an excellent cleaning quality.

The configuration according to claim 9 in an advantageous manner ensuresthat a simple and cost-effective structure of the cleaning device isachieved.

In the configuration according to claim 10, another advantage alsoresides in that, due to the angular orientation of the welding torch orgas nozzle relative to the brush, cleaning of a specially designed gasnozzle having a conically tapering shape is feasible.

A configuration according to claims 11 and 12 is also advantageous,since thereby shorter cleaning times will be obtained.

Yet, also a configuration according to claims 13 to 17 is of advantage,since is ensures the achievement of an excellent cleaning quality onaccount of the bristles being adaptable to the shape of the gas nozzleand, hence, permanently contacting the surfaces to be cleaned.

A configuration according to claim 18 is, however, also advantageous,since it prevents extensive pressing apart of the bristles.

The present invention will be explained in more detail by way of theaccompanying drawings. Therein:

FIG. 1 is a partial cutout of a welding torch in a sectional andsimplified, schematic illustration;

FIG. 2 is a side view of a brush for a cleaning device in a simplified,schematic illustration;

FIG. 3 is a top view on the brush in a simplified, schematicillustration;

FIG. 4 is a section through a bristle of the brush in a simplified,schematic illustration.

FIG. 1 shows a cutout and, in particular, an end region associated withthe welding process, of a welding torch 1. The welding torch 1 comprisesa gas nozzle 2, a nozzle assembly 3 and a contact tube 4. The otherparts of the welding torch 1 have been omitted for the sake of clarity.Also is the structure or configuration of the illustrated parts notlimited to the exemplary embodiment shown, and it is feasible to applythe solution according to the invention to any welding torch 1 knownfrom the prior art, or parts thereof.

The gas nozzle 2 illustrated in FIG. 1 is made of copper or a copperalloy and detachably fastened to the welding torch 1. The contact tube 4as well as the nozzle assembly 3, which are provided in variousconfigurations in every welding torch, are likewise made of copper or acopper alloy, the contact tube 4 being detachably connected with thenozzle assembly 3. The description of the mode of functioning of thesecomponents and their tasks has been omitted, since these aresufficiently well-known from the prior art.

As already mentioned in the beginning, weld spatters 5 are formed duringa welding process as schematically illustrated, which deposit on the gasnozzle 2, contact tube 4 and nozzle assembly 3 and remain adhering tothese components. In longer-lasting welding processes it may, thus,happen that the welding torch 1 is partially or fully obstructed by suchweld spatters 5 and the gas flow will consequently become irregular orcompletely interrupted, with the formation of short-circuits between theindividual components being feasible. Since in conventional gas nozzles2 made of copper, or the copper parts of a welding torch 1, the weldspatters 5 burn into the surface or melt to the same, it is frequentlydifficult to clean these parts because of the firm adherence and, hence,difficult separation of the weld spatters 5.

If, to make things worse, the welding torch 1 is used for aluminumwelding, cleaning of the copper parts, particularly of the nozzleassembly 3 and the contact tube 4, or the gas nozzle 2, respectively,will be even more difficult, because aluminum weld spatters cannot besimply blast off or peeled off during cleaning. Aluminum weld spatters 5have the property of not readily separating as a whole during cleaningbut, due to the softness of the material, rather being smeared or spreadby rubbing, which means that aluminium weld spatters 5 cannot be removedas a whole during cleaning by known cleaning devices such as, forinstance, milling devices or brush devices including steel bristles, butare rather peeled off by such cleaning devices, thus being smeared orspread by rubbing.

Especially robotic applications effect automated cleaning of the weldingtorch 1, so that it has to be ensured that the weld spatters 5 areremoved to the largest extent possible. To this end, a special tool 6,particularly a brush 7, for cleaning the welding torch 1 is described inmore detail in FIGS. 2 to 4, which cleaning device is highly suitableespecially for aluminum welding processes in connection with theconfiguration according to the invention of the gas nozzle 2 or weldingtorch 1, respectively, and, in particular, the nozzle assembly 3 and thecontact tube 4.

The solution according to the invention now contemplates that thewelding torch parts made of copper or copper alloys are speciallytreated with a view to reducing the stickability of weld spatters 5,i.e., strongly reducing spatter adherence. To this end, these parts and,in particular, the gas nozzle 2, the contact tube 4 and the nozzleassembly 3 are provided with an artificially produced patina layer 8.

A patina layer 8 will basically form by oxidation, if copper is exposedto the atmosphere over an extended period of time, yet such a patinalayer 8 will only form after about 10 years. However, since such a longstorage time enabling the build-up of a patina layer 8 is unprofitable,the parts are subjected to an artificial aging process to rapidly formsaid patina layer 8 within an extremely short time. The patina layer 8,in principle, is comprised of basic copper compounds, particularlycopper carbonates and/or sulfates, which are formed by the reaction ofcopper with carbon or sulfur dioxides. The patina layer 8 has theproperty that, with the employment of such parts in an aluminum weldingprocess, these will not combine with the aluminum, i.e., the aluminumweld spatters 5, so that the weld spatters 5 will be prevented fromburning into, or melting to, the surface, thus providing a sealingprotection. When using a patina layer 8, the spatter adherence isreduced by a factor of 5 to 10, whereby the service lives too of suchparts provided with patina layers 8 will be substantially increased. Theformation of a patina layer 8 also offers substantial advantages in thecleaning of such parts, because the weld spatters 5 will no longer burninto the surfaces of these parts, or melt to the same, so as to enablesimple cleaning without causing damage to the surfaces of these parts.

Various modes of procedure may be envisaged to produce the patina layer8. One way of producing an artificial patina layer 8 on the gas nozzle 2and/or the nozzle assembly 3 and/or the contact tube 4 is describedbelow. The copper parts are successively immersed into two solutions.The first solution is comprised of 1 liter water and 2 ml sulfuratedpotash. The second solution comprises again 1 liter water, 1 to 2 gcopper sulfate and 10 ml sulfuric acid. The copper parts on which anartificial patina layer 8 is to be produced are then immersed into thefirst solution for some seconds. After this, the copper parts are rinsedand immersed into the second solution. This procedure is repeatedseveral times, particularly 2 to 3 times. This procedure causes thecopper part to change color thus forming the patina layer 8, saiddiscoloration or patina layer 8 adhering very firmly to the parent metalof the copper parts, i.e., the gas nozzle 2, the nozzle assembly 3 andcontact tube 4.

The patina layer 8 will be the thicker the more frequently thisprocedure is repeated. In a preferred manner, the patina layer 8 has athickness ranging between 50 and 200 μm.

The patina layer 8 is at least provided on a partial region of thesurface of the gas nozzle 2, which means that the patina layer 8 isformed at least in that area which is to be protected from weld spatter5. The use of such gas nozzles 2, or the welding torch 1, with thepatina layer 8 is recommended for aluminum welding processes as well asMIG soldering. It is, of course, feasible to use the welding torch 1 orgas nozzle 2 in other welding or soldering methods too.

FIGS. 2 to 4 depict a cleaning device, wherein the overall structure ofthe cleaning device is not illustrated, but only a tool 6 in the form ofa brush 7. The cleaning device, for instance, comprises a housing whichis designed like a box, in which all components provided for thecleaning of the welding torch 1, such as, for instance, a control unit,drive motors, monitoring means, interfaces for the connection toexternal components such as, for instance, a welding apparatus and/or arobot etc. are contained.

The cleaning device for the welding torch 1 and, in particular, its gasnozzle 2, nozzle assembly 3 and contact tube 4, which comprise a coatingand, in particular, a patina layer 8 has been specifically designed foruse in an aluminum welding process, which means that the parts to bewelded consist of aluminum or aluminum alloys and an aluminum weldingwire is used in the welding apparatus. For the cleaning of the gasnozzle 2 or welding torch 1, the cleaning device comprises the rotatingtool 6 and, in particular, the brush 7, which is mechanically driven viaa drive motor (not illustrated). The tool 6 is designed to beexchangeable in a simple manner. In order to clean the welding torch 1and the gas nozzle 2, these are approached to the tool 6, and the gasnozzle 2 and welding torch 1 are freed of weld spatters 5 by therotating tool 6. The approach of the welding torch 1 is preferablycarried out by a robot. However, it is, of course, also feasible to usesuch a cleaning device manually, i.e., the welding torch 1 plus the gasnozzle 2 mounted thereto are manually brought to the tool 6 by a user.

In order to reach a high cleaning quality, the bristles 9 of the brush 7are made of a very soft, elastic material, preferably a syntheticmaterial. The bristles 9 are, moreover, provided with a coating 10 inwhich abrasives 11 are embedded. In a preferred manner, the bristles 9of the brush 7 are comprised of one, or a combination, of the materialssilicon carbide, polyvinyl chloride, nylon, polyamide, polypropylene,polyethylene or fibre. It will be of advantage if the bristles 9 aredesigned to be corrugated and, if desired, additionally plaited.

The brush 7 is preferably constructed in a manner that the diameter 12,or outer periphery, of the brush 7 is larger than the diameter 13, orouter periphery, of the gas nozzle 2 of the welding torch 1. It isthereby ensured that a portion of the bristles 9 of the brush 7 are ableto reach into the interior of the gas nozzle 2 while, at the same time,bristles 9 contact the outer surface of the gas nozzle 2, so that thesimultaneous cleaning of the interior and the outer surface of the gasnozzle 2 is carried out in a single operation. The bristles 9 of thebrush 7 preferably have a length ranging between 15 mm and 50 mm.

In the cleaning device or tool 6 illustrated in FIG. 5, the gas nozzle 2is oriented relative to the brush 7 in a manner that the central axis 14of the brush 7 is arranged in alignment with the central axis 15 of thegas nozzle 2 and the welding torch 1, respectively. In the furtherexemplary embodiment according to FIG. 6, the gas nozzle 2, and weldingtorch 1, are oriented relative to the brush 7 in a manner that thecentral axis 14 of the brush 7 is arranged relative to the central axis15 of the gas nozzle 2 at an angle 16 of between 120° and 160°.

In a preferred manner, the welding torch 1 and the brush 7 perform arotational movement, with a diametrically opposed movement beingpreferred. It is, however, also feasible that only one of the twoelements and, in particular, the brush 7, carries out a rotationalmovement. In the event of an angularly arranged welding torch 1according to FIG. 6, the welding torch 1 carries out an eccentricrotational movement. It is, thus, ensured in an an advantageous mannerthat the the bristles 9 are able to adapt to the shape of the gas nozzle2 in the interior of the gas nozzle 2. It is, thereby, feasible to cleanalso those gas nozzles 2 which have conically tapering shapes. Theangular arrangement of the gas nozzle 2 relative to the bristles 9, infact, causes the bristles 9 to contact the gas nozzle 2 along itsconically tapering extension. If a perpendicular orientation were usedwith such conically tapering gas nozzles 2, the bristles 9 would enterthrough the opening of the gas nozzle 2 yet not extend along the innerwall of the gas nozzle 2, so that only limited cleaning, i.e., cleaningof the end regions of the gas nozzle 2 and the contact tube 4 and thenozzle assembly 3 would be feasible.

It is, furthermore, feasible that the brush 7 and, in particular, thebristles 9 have different shapes. The bristles 9 may, for instance, havedifferent lengths, with different coherent regions being preferablyprovided. In this connection, it is possible to make the bristles 9 in aregion in the center of the brush 7 shorter than in the peripheral edgeregion. It is also possible to provide shorter bristles 9 in the regionof the brush 7, that is congruent with the housing of the gas nozzle 2.Another option would be to arrange a projection in the edge region ofthe brush 7, which projection is difficult to elastically deform so asto allow for only slight pressing apart of the bristles 9 as the latterare being pressed or forced on the gas nozzle 2 or welding torch 1.

It is essential to the cleaning device according to the invention thatthe brushes 7, or synthetic brushes, are constructed in a manner thatabrasives 11 are incorporated in the bristles 9, wherein new grain orabrasives 11 are constantly released by the wear of the brushes 7 so asto ensure a uniform grinding effect. The synthetic brushes are highlyelastic and flexible, thus allowing for better cleaning than metalbrushes on sites that are difficult to accede, such as the interior ofthe welding torch. Moreover, the surfaces of the parts to be cleanedsuch as, for instance, the gas nozzle 2, the contact tube 4, the nozzleassembly 3 etc. will not become as heavily damaged or scratched as bymetal brushes known from the prior art. If the surface is heavilyscratched, weld spatter 5 will even better adhere in a welding processthan in the event of a smooth surface.

1: A gas nozzle for a welding torch, which is made of copper or a copperalloy, comprising an artificially produced patina layer (8) at least ona partial area of its surface. 2: A welding torch including a gasnozzle, a nozzle assembly and a contact tube, wherein the gas nozzleand/or the nozzle assembly and/or the contact tube are made of copper ora copper alloy, the gas nozzle (2) and/or the nozzle assembly (3) and/orthe contact tube (4) comprising an artificially produced patina layer(8) at least on a partial area of the respective surface. 3: A gasnozzle and a welding torch according to claim 1, wherein said patinalayer (8) has a thickness ranging between 50 and 200 μm. 4: A gas nozzleand a welding torch according to claim 1, wherein said patina layer (8)is provided over the entire surface. 5: A cleaning device for a weldingtorch and, in particular, its gas nozzle, which includes a brushprovided with bristles for cleaning the welding torch of weld spatter,wherein the bristles (9) of the brush (7) are formed of a very soft,elastic material, preferably a synthetic material, and that abrasives(11) are embedded in the bristles (9). 6: A cleaning device according toclaim 5, wherein the bristles (9) are provided with a coating (10) inwhich said abrasives (11) are embedded. 7: A cleaning device accordingto claim 5, wherein the diameter (12), or outer periphery, of the brush(7) is larger than the diameter (13), or outer periphery, of the gasnozzle (2) of the welding torch (1). 8: A cleaning device according toclaim 5, wherein the bristles (9) of the brush (7) have a length rangingbetween 15 mm and 50 mm. 9: A cleaning device according to claim 5,wherein the central axis (14) of the brush (7) in the cleaning positionis arranged in alignment with the central axis (15) of the gas nozzle(2) and welding torch 1, respectively. 10: A cleaning device accordingto claim 5, wherein the central axis (14) of the brush (7) in thecleaning position encloses an angle (16) of between 120° and 160° withthe central axis of the gas nozzle (2) and welding torch (1),respectively. 11: A cleaning device according to claim 5, wherein thebrush (7) carries out a rotational movement in respect to the gas nozzle(7) and welding torch (1), respectively, preferably in the counterdirection to an optional rotational movement of the gas nozzle (7) andwelding torch (1), respectively. 12: A cleaning device according toclaim 11, wherein the brush (7) carries out an eccentric rotationalmovement. 13: A cleaning device according to claim 5, wherein thebristles (9) have different lengths with different coherent regionsbeing preferably provided. 14: A cleaning device according to claim 13,wherein the bristles (9) in a region in the center of the brush (7) areshorter than in the peripheral edge region or vice versa. 15: A cleaningdevice according to claim 13, wherein the region of the brush (7)corresponding to the projection of the gas nozzle (2) has shorterbristles (9) than the remaining region of the brush (7). 16: A cleaningdevice according to claim 5, wherein the bristles (9) of the brush (7)are comprised of one, or a combination, of the materials siliconcarbide, polyvinyl chloride, nylon, polyamide, polypropylene,polyethylene or fibre. 17: A cleaning device according to claim 5,wherein the bristles (9) are designed to be corrugated or plaited. 18: Acleaning device according to claim 5, wherein a projection surroundingthe bristles (9) over a partial region of their length is arranged inthe edge region of the brush (7).